Exciton localization by clusters in diluted bulk InGaN and two-dimensional CdZnSe solid solutions

Abstract : The photoluminescence (PL) bands of MOCVD grown double heterostructures (DHS) GaN/InGaN/GaN with In constant in the range 0.4-2% as well as MEE grown ZnSe/CdSe/ZnSe QWs with 0.3-1.5 ML CdSe nominal thicknesses show a fine structure which can be attributed to small In or Cd clusters respectively occurring in cations sublattices at random filling of the lattice sites. This fine structure is smoothed away at further concentration increase in both systems. At the lowest concentration the excitons motion in these systems has a character of 3D and 2D percolation over the "impurity" bands formed by clusters of size s = 2 in both cases. We have found that similarity of InGaN and ZnCdSe PL-band shapes despite the different dimensionality of objects (3D DHS and 2D QWs) is due to a different perturbation strength produced by In and Cd respectively.